A quantitative model of the magnetosphere with poloidal vector fields

Kosik, J. C.

doi:10.1007/s00585-998-1557-9

Cited by 4 publications

(1 citation statement)

References 18 publications

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“…In its general features, such an approach was outlined in a review by Stern []. Kosik [, ] developed a data‐based model which included only the poloidal component, with the generating function Ψ 2 being limited to a sum of a few spherical harmonics.…”

Section: Methods Descriptionmentioning

confidence: 99%

Reconstructing the magnetosphere from data using radial basis functions

Andreeva

Tsyganenko

2016

JGR Space Physics

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A new method is proposed to derive from data magnetospheric magnetic field configurations without any a priori assumptions on the geometry of electric currents. The approach utilizes large sets of archived satellite data and uses an advanced technique to represent the field as a sum of toroidal and poloidal parts, whose generating potentials Ψ1 and Ψ2 are expanded into series of radial basis functions (RBFs) with their nodes regularly distributed over the 3‐D modeling domain. The method was tested by reconstructing the inner and high‐latitude field within geocentric distances up to 12RE on the basis of magnetometer data of Geotail, Polar, Cluster, Time History of Events and Macroscale Interactions during Substorms, and Van Allen space probes, taken during 1995–2015. Four characteristic states of the magnetosphere before and during a disturbance have been modeled: a quiet prestorm period, storm deepening phase with progressively decreasing SYM‐H index, the storm maximum around the negative peak of SYM‐H, and the recovery phase. Fitting the RBF model to data faithfully resolved contributions to the total magnetic field from all principal sources, including the westward and eastward ring current, the tail current, diamagnetic currents associated with the polar cusps, and the large‐scale effect of the field‐aligned currents. For two main phase conditions, the model field exhibited a strong dawn‐dusk asymmetry of the low‐latitude magnetic depression, extending to low altitudes and partly spreading sunward from the terminator plane in the dusk sector. The RBF model was found to resolve even finer details, such as the bifurcation of the innermost tail current. The method can be further developed into a powerful tool for data‐based studies of the magnetospheric currents.

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Section: Methods Descriptionmentioning

confidence: 99%

Reconstructing the magnetosphere from data using radial basis functions

Andreeva

Tsyganenko

2016

JGR Space Physics

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Modeling the inner magnetosphere: The asymmetric ring current and Region 2 Birkeland currents revisited

Tsyganenko¹

2000

J. Geophys. Res.

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Abstract. A quantitative model is developed of the inner magnetospheric magnetic field, combining the effects of the azimuthally asymmetric ring current with those of field-aligned currents, due to azimuthal variation of the plasma pressure. The axisymmetric part of the model ring current was derived from average observed radial profiles of the particle pressure and anisotropy and was analytically represented by a vector potential, fitted by least squares to one derived by the Biot-Savart integral. The contribution of the asymmetric part, including the field of Birkeland currents, closed via the ionosphere, was represented as a divergenceless combination of expansions for the components of the B vector, and was also fitted by least squares to the corresponding Biot-Savart field. The total field-aligned current, associated with the noon-midnight pressure asymmetry of the outer ring current, was found to be significantly smaller than the total Region 2 current, observed at low altitudes. It is therefore concluded that most of that current is generated in the near-Earth plasma sheet. The goal of this work is a realistic and computationally efficient description of the asymmetric ring current, to be included in an advanced model of the external geomagnetic field.

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How to determine the thermal electron density and the magnetic field strength from the Cluster/Whisper observations around the Earth

et al. 2001

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Abstract. The Wave Experiment Consortium, WEC, is a highly integrated package of five instruments used to study the plasma environment around the Earth. One of these instruments, the Waves of HIgh frequency and Sounder for Probing of Electron density by Relaxation, Whisper, aims at the thermal electron density evaluation and natural wave monitoring in the 4-83 kHz frequency range. In its active working mode, which is our primarily concern here, the Whisper instrument transmits a short wave train at a swept frequency and receives echoes after a delay. Incidentally, it behaves like a classical ground-based ionosonde. Natural modes of oscillations may thus be excited in the surrounding medium. This means that with suitable interpretations, the Whisper sounding technique becomes a powerful tool for plasma diagnosis. By taking into account the characteristic frequencies of the magnetoplasmas encountered by the Cluster spacecraft, it is indeed possible to reliably and accurately determine the electron density and, to a lesser degree, the magnetic field strength from the Whisper electric field measurements. Due to the predominantly electrostatic nature of the waves that are excited, observations of resonances may also lead to information on the electron velocity distribution functions. The existence of a hot population may indeed be revealed and the hot to cold density ratio can be estimated.

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A quantitative model of the magnetosphere with poloidal vector fields

Cited by 4 publications

References 18 publications

Reconstructing the magnetosphere from data using radial basis functions

Reconstructing the magnetosphere from data using radial basis functions

Modeling the inner magnetosphere: The asymmetric ring current and Region 2 Birkeland currents revisited

How to determine the thermal electron density and the magnetic field strength from the Cluster/Whisper observations around the Earth

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